PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU DEC 16 2004 . . . . . . . . SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS CURRENT OBSERVATIONS INDICATE THAT WEAK WARM EPISODE CONDITIONS (EL NINO) CONTINUE OVER THE EQUATORIAL PACIFIC AND A MAJORITY OF SEA SURFACE TEMPERATURE (SST) PREDICTION TOOLS INDICATE THAT AT LEAST WEAK EL NINO CONDITIONS WILL CONTINUE THROUGH THE FIRST FEW MONTHS OF 2005. THERE IS A SMALL CHANCE THAT THE EL NINO COULD STRENGTHEN TO MODERATE INTENSITY BUT ALSO A CHANCE THAT IT WILL WEAKEN BACK TO NEUTRAL STATUS. HOWEVER THE CONSENSUS AMONG STATISTICAL AND DYNAMICAL MODEL PREDICTIONS CONTINUES TO INDICATE THAT THREE-MONTH AVERAGED SST ANOMALIES IN THE CENTRAL EQUATORIAL PACIFIC AVERAGED OVER THE REGION BOUNDED BY 120W TO 170W AND WITHIN 5 DEGREES OF THE EQUATOR (NINO 3.4 REGION) WILL MOST LIKELY REMAIN IN THE RANGE OF +0.5 TO +1.0 DEG C THROUGH MAM 2005. AFTER MAM 2005 THE OUTLOOK BECOMES MORE UNCERTAIN... BUT MOST MODELS INDICATE A WEAKENING AND END OF THE WARM EPSIODE LATER IN 2005 WITH SOME RESIDUAL WARMTH REMAINING. BASIN-WIDE... OR CLASSICAL STRONG EL NINOS LIKE THOSE OF 1982-83 AND 1997-98 HAVE A PATTERN OF WARM SST ANOMALIES WHICH EXTEND ALL THE WAY FROM THE DATE LINE TO THE COAST OF PERU. IMPACTS OF SUCH EL NINOS OFTEN INCLUDE ABOVE AVERAGE WETNESS FROM CALIFORNIA TO FLORIDA ASSOCIATED WITH AN ACTIVE SUBTROPICAL JET STREAM AND EASTWARD EXTENSION OF THE PACIFIC JET...RESPECTIVELY...AND UNUSUAL DRYNESS IN THE NORTHWEST AND THE OHIO VALLEY. THESE EVENTS ARE ALSO CHARACTERIZED BY WARM TEMPERATURE ANOMALIES ACROSS THE NORTHERN TWO-THIRDS OF THE CONTINENTAL U.S. CENTRAL PACIFIC EL NINOS...LIKE THOSE IN 1963-64, 1968-69 AND 2002-03 ARE CHARACTERIZED BY SMALL SST ANOMALIES IN THE EASTERN PACIFIC AND WARM SST ANOMALIES IN THE CENTRAL TROPICAL PACIFIC. THE U.S. TEMPERATURE RESPONSE TO THIS TYPE OF EL NINO IS USUALLY COLDER THAN NORMAL OVER THE SOUTHEAST AND A MUCH LESS RELIABLE HEAVY PRECIPITATION SIGNAL ACROSS THE SOUTHERN U.S. .. ESPECIALLY IN CALIFORNIA. . . . . . . . . SOME EL NINO-RELATED INFLUENCE ON U.S. CLIMATE IS LIKELY FOR THE UPCOMING WINTER... AND A SLIGHT INCREASE IN THE ODDS IN FAVOR OF EL NINO IMPACTS ARE INDICATED IN THE LONG-LEAD OUTLOOKS BETWEEN JFM AND MAM 2005. FOR LEAD TIME BEYOND MAM 2005 THE OUTLOOK PRIMARILY REFLECTS LONG TERM TEMPERATURE AND PRECIPITATION TRENDS. . . . . . . . . THE OUTLOOK FOR JFM 2005 THROUGH AMJ 2005 IS BASED ON THE CFS MODEL FROM NCEP... THE MULTI-MODEL ENSEMBLE FROM IRI...A STATISTICAL MULTI-MODEL ENSEMBLE FORECAST FROM CDC AND CCA OCN AND TREND ADJUSTED ENSO COMPOSITES FROM CPC. OCN IS THE PRIMARY TOOL FOR AMJ 2005-JFM 2006. WE NOTE THAT THE CFS HAS BECOME MORE LIKE A CANONICAL WARM EVENT THAN 1 MONTH AGO. IN GENERAL CHANGES FROM ONE MONTH AGO ARE SMALL. THERE IS VERY GOOD AGREEMENT AMONG ALL OF THE DYNAMICAL AND STATISTICAL MODELS ON BOTH THE LARGE-SCALE CIRCULATION AND TEMPERATURE AND PRECIPITATION FORECASTS DURING THE WINTER SEASONS... MAKING THIS FORECAST WELL-SUPPORTED BY THE FORECAST TOOLS. FOR MAM 2005 AND BEYOND THE FORECAST REFLECTS ONLY TRENDS TOWARDS WARMER THAN NORMAL TEMPERATURES OVER MUCH OF THE WEST IN THE SPRING... AND OVER THOSE REGIONS AS WELL AS THE SOUTHEASTERN U.S. IN SUMMER... AND ABOVE NORMAL TEMPERATURES EXTENDING INTO SOUTH FLORIDA AND THE SOUTHWESTERN U.S. IN THE FALL. . . . . . . . . PRECIPITATION FOR JFM 2005 REFLECTS THE FORECAST TOOLS AND IS CONSISTENT WITH WEAK EL NINO CONDITIONS. BOTH THE WET SIGNAL OVER THE SOUTHERN PLAINS AND THE DRY SIGNAL OVER THE OHIO VALLEY ARE OFTEN ASSOCIATED WITH WEAK EL NINOS. THE PRECIPITATION FORECAST FOR THE SOUTHWESTERN U.S. FAVORS AN INCREASING CHANCE OF ABOVE NORMAL PRECIPITATION DURING LATE WINTER AND ESPECIALLY DURING THE EARLY SPRING. FROM AMJ 2005 THROUGH NDJ 2005 THE OUTLOOK REFLECTS PRECIPITATION TRENDS... WHICH ARE GENERALLY MODEST. . . . . . . . . BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS CURRENT OCEANIC AND ATMOSPHERIC CONDITIONS INDICATE THAT WEAK EL NINO CONDITIONS NOW EXIST IN THE CENTRAL TROPICAL PACIFIC. NOAAS DEFINITION OF EL NINO CONDITIONS REQUIRES THAT 3-MONTH RUNNING MEAN SST ANOMALIES IN THE NINO 3.4 REGION - BETWEEN 120W TO 170W AND WITHIN 5 DEGREES OF THE EQUATOR - EXCEED +0.5 DEGREES CELSIUS. THIS HAS BEEN THE CASE SINCE JAS. THE MOST RECENT WEEKLY MEAN SHOWS THAT SSTS ARE NEAR 1 C ABOVE NORMAL ALONG AND NEAR THE EQUATOR FROM 160E TO 135W. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS A CONSOLIDATION OF DYNAMICAL AND STATISTICAL NINO 3.4 SST FORECASTS INDICATES THAT NINO 3.4 SST ANOMALIES WILL REMAIN CLOSE TO 1 DEGREES C THROUGH WINTER INTO SPRING BEFORE SLOWLY DECREASING IN THE LATE SPRING AND SUMMER MONTHS OF 2005. ENSEMBLE PREDICTIONS FROM THE NEW CFS MODEL... AND STATISTICAL PREDICTIONS FROM CCA... CA... AND THE MKV MODEL PREDICT THE NINO 3.4 SSTS ANOMALIES IN AN ENVELOPE BETWEEN +0.3 AND +1.2 DEGREES C THROUGH MAM 2005... WITH MOST BETWEEN 0.5 AND 1.0 DEG C. SMALL POSITIVE ANOMALIES MAY PERSIST UNTIL NEXT WINTER. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE OUTLOOK FOR JFM 2005 THROUGH AMJ 2005 IS BASED ON THE CFS MODEL FROM NCEP... THE MULTI-MODEL ENSEMBLE FROM IRI...A STATISTICAL MULTI-MODEL ENSEMBLE FORECAST FROM CDC AND CCA OCN AND TREND ADJUSTED ENSO COMPOSITES FROM CPC. OCN IS THE PRIMARY TOOL FOR AMJ 2005-JFM 2006. WE NOTE THAT THE CFS HAS BECOME MORE LIKE A CANONICAL WARM EVENT THAN 1 MONTH AGO. IN GENERAL CHANGES FROM ONE MONTH AGO ARE SMALL. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2005 TO JFM 2006 TEMPERATURE: FOR JFM THROUGH MJJ 2005 THE FORECAST TOOLS VERY CONSISTENTLY PREDICT ENHANCED LIKELIHOOD OF ABOVE NORMAL TEMPERATURES IN THE WESTERN U.S AND ALASKA. ENHANCED LIKELIHOOD OF SUBNORMAL TEMPERATURES IS PREDICTED FOR JFM AND FMA IN THE SOUTHEASTERN OR SOUTHERN U.S.... WHILE UNCERTAIN CONDITIONS PREVAIL FROM THE CENTRAL U.S. TO NEW ENGLAND. WE MADE THE LARGEST CHANGES IN SPRING AND ADDED A STRIP OF BELOW NORMAL TEMPERATURES FROM TEXAS TO THE DAKOTAS. THE NORTHERN PORTION CAN BE JUSTIFIED BY OCN WHILE ENSO, CDC, CAS AND EXPECTATIONS OF WET SOIL JUSTIFY COLD IN THE SOUTH. . . . . . . . . PRECIPITATION: FORECAST TOOLS ARE IN GOOD AGREEMENT ON THE MAIN FEATURES OF THE FORECAST... INCLUDING ENHANCED LIKELIHOOD OF ABOVE-MEDIAN PRECIPITATON FROM CALIFORNIA... ACROSS THE SOUTHWEST AND TEXAS... ALONG THE GULF COAST TO FLORIDA IN JFM AND FMA... WITH ENHANCED ODDS OF ABOVE-MEDIAN PRECIPITATON RETREATING TO MAINLY THE SOUTHWEST BY MAM. ENHANCED LIKELIHOOD OF SUB-MEDIAN PRECIPITATION IS PREDICTED FOR THE NORTHWEST AND THE OHIO VALLEY IN JFM AND FMA. FROM AMJ 2005 THROUGH JFM 2006 OCN GIVES MAINLY WEAK INDICATIONS FOR PERSISTENT REGIONS OF ENHANCED LIKELIHOOD OF DRYNESS IN THE NORTHWEST...FROM JJA 2005-ASO 2005... AND FOR INCREASED ODDS OF EXTRA WETNESS IN THE SOUTH- CENTRAL U.S. FROM OND 2005-DJF 2005-06. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . FORECASTER: H. VAN DEN DOOL GLOSSARY AND DEFINITIONS: ANALOG (NATURAL ANALOG) - A WEATHER MAP THAT RESEMBLES ANOTHER WEATHER MAP - USUALLY FROM DIFFERENT YEARS BUT THE SAME SEASON IN THE HISTORICAL RECORD. THE CRITERION FOR SELECTING AN ANALOG IS OFTEN THE PATTERN CORRELATION BETWEEN THE MAPS. TWO MAPS WILL JUST BEGIN TO RESEMBLE EACH OTHER TO THE HUMAN EYE AT A PATTERN CORRELATION OF ABOUT 40%. TO BE USEFUL - ANALOGS NEED TO HAVE MUCH HIGHER CORRELATIONS TO THE ORIGINAL MAP THAN THAT - 80% OR MORE. ANALOGS ARE INCREASINGLY DIFFICULT TO FIND AS THE GEOGRAPHIC REGION BEING COMPARED INCREASES IN SIZE. PERFECT ANALOGS TO THE ENTIRE NORTHERN HEMISPHERE SIMPLY DO NOT EXIST - FOR PRACTICAL PURPOSES. THIS IS WHY SIMPLE ANALOG FORECAST METHODS DO NOT WORK VERY WELL. ANNUAL CYCLE - AT MOST LOCATIONS THE CLIMATE STATE VARIABLES - T - P - SST- WIND - AND OTHERS DISPLAY A REGULAR VARIATION WHICH FOLLOWS THAT OF THE ELEVATION OF THE SUN IN THE SKY. A GRAPH OF THE 30 YEAR AVERAGE OF A VARIABLE FOR EACH DAY OF THE YEAR VERSUS DATE SHOWS A WAVE-FORM WHICH - FOR T AT DES MOINES FOR EXAMPLE - RANGES SMOOTHLY FROM LOWEST VALUES IN THE WINTER TO HIGHEST VALUES IN THE SUMMER. ANOMALY - THE ARITHMETIC DIFFERENCE BETWEEN THE VALUE OF A VARIABLE AT A GIVEN PLACE AND TIME AND THE LONG-TERM AVERAGE (USUALLY 30 YEARS) FOR THE LOCATION AND TIME OF YEAR. AO - ARCTIC OSCILLATION - A MEASURE OF THE DIFFERENCE IN PRESSURE (AT SEA LEVEL) OR 500-HPA HEIGHT (IN THE MIDDLE TROPOSPHERE) BETWEEN THE NORTHERN POLAR REGION AND MIDDLE LATITUDES. WHEN PRESSURES AND HEIGHTS ARE ABOVE (BELOW) NORMAL AT HIGH LATITUDES AND BELOW (ABOVE) NORMAL AT MIDDLE LATITUDES - THE AO IS DEFINED AS NEGATIVE (POSITIVE) AND IS ASSOCIATED WITH BELOW (ABOVE) NORMAL TEMPERATURES OVER MIDDLE LATITUDES - INCLUDING THE CONUS. CA - CONSTRUCTED ANALOG - A LINEAR COMBINATION OF PAST OBSERVED ANOMALY PATTERNS SUCH THAT THE COMBINATION IS AS CLOSE AS DESIRED TO THE INITIAL STATE. A FORECAST IS OBTAINED BY PERSISTING THE WEIGHTS ASSIGNED TO EACH YEAR IN THE HISTORICAL RECORD AND LINEARLY COMBINING THE STATES FOLLOWING THE INITIAL TIME IN THE HISTORICAL YEARS. CAS - CONSTRUCTED ANALOG SOIL MOISTURE PREDICTION TECHNIQUE. CCA - CANONICAL CORRELATION ANALYSIS - A TECHNIQUE WHICH PREDICTS THE STATUS OF U.S. T AND P FOR SOME FUTURE TARGET SEASON USING THE MOST RECENT 4 NON- OVERLAPPING SEASONAL OBSERVATIONS OF TROPICAL PACIFIC SST - CIRCULATION AND U.S. T OR P TO CHARACTERIZE THE RECENT BEHAVIOR OF THE CLIMATE - AND PAST OBSERVATIONS TO PLACE RECENT BEHAVIOR INTO A HISTORICAL CONTEXT. CLIMATOLOGY - THE 30-YEAR AVERAGE OF A VARIABLE - LIKE TEMPERATURE - AT A GIVEN LOCATION AND TIME OF YEAR. . . . . . . . . CONUS - CONTERMINOUS UNITED STATES DYNAMICAL MODEL - A PREDICTION METHOD WHICH USES EQUATIONS DESCRIBING THE PHYSICAL BEHAVIOR OF A SYSTEM AND A COMPREHENSIVE SET OF CURRENT OBSERVATIONS OF THE VALUES OF THE VARIABLES DESCRIBING THE CURRENT STATE OF THE SYSTEM (INITIAL CONDITIONS) TO PREDICT THE VALUES OF THOSE VARIABLES A SHORT TIME-STEP IN THE FUTURE. THOSE VALUES ARE - IN TURN - USED AS THE INITIAL CONDITIONS FOR A SUBSEQUENT PREDICTION - AND SO ON - UNTIL THE DESIRED FUTURE PREDICTION TIME IS REACHED. EASTERLY WIND - WIND BLOWING FROM EAST TO WEST. EC - EQUAL CHANCES - THE PROBABILITY OF THE MOST LIKELY CATEGORY CANNOT BE DETERMINED AND THE EXPECTED LIKELIHOODS OF ABOVE - NORMAL AND BELOW DO NOT DIFFER FROM THEIR CLIMATOLOGICAL ODDS OF 33 1/3% EACH. EC REPLACES CL. EL NINO - THE WARM PHASE OF THE ENSO CYCLE ENSO - ACRONYM FOR EL NINO/SOUTHERN OSCILLATION GCM - GENERAL CIRCULATION MODEL - A GENERIC TERM APPLIED TO GLOBAL DYNAMICAL MODELS. ITCZ - INTERTROPICAL CONVERGENCE ZONE - A LINE WHERE THE SOUTHEASTERLY AND NORTHEASTERLY TRADE WINDS CONVERGE - CHARACTERIZED BY ENHANCED CONVECTION. IT MAY BE IN EITHER THE NORTHERN OR SOUTHERN HEMISPHERE - AND OCCASIONALLY A DOUBLE ITCZ MAY BE SEEN IN BOTH HEMISPHERES NOT FAR FROM THE EQUATOR. LA NINA - THE COLD PHASE OF THE ENSO CYCLE MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLATION - A DISTURBANCE IN TROPICAL CONVECTION - PRECIPITATION - WIND AND PRESSURE. MJO PRECIPITATION AND CLOUDINESS ARE ENHANCED ONLY IN REGIONS WHERE SSTS ARE VERY WARM - E.G. INDIAN OCEAN AND WEST PACIFIC. THE PRESSURE AND WIND DISTURBANCE ASSOCIATED WITH MJO IS OBSERVED TO MOVE FROM WEST TO EAST COMPLETELY AROUND THE GLOBAL TROPICS IN ABOUT 30 TO 60 DAYS. NAO - NORTH ATLANTIC OSCILLATION TELECONNECTION PATTERN - WHICH MAY BE CONSIDERED AS THE ATLANTIC HALF OF THE AO. NOTE THAT THE STATUS OF THE AO/NAO AND OTHER SLOWLY VARYING CIRCULATION MODES - WHILE VERY IMPORTANT IN DETERMINING THE TEMPERATURE AND PRECIPITATION REGIMES OVER THE U.S. - ARE UNPREDICTABLE BEYOND A WEEK OR TWO AHEAD AT BEST BY CURRENT TECHNOLOGY AND ARE NOT EXPLICITLY INCLUDED IN OUR FORECAST PROCESS AS RELIABLE PREDICTORS. NORTHERLY WIND - WIND BLOWING FROM NORTH TO SOUTH. OCN - OPTIMAL CLIMATE NORMALS - A FORECAST BASED ON PERSISTING THE AVERAGE OF THE LAST 10 YEARS FOR TEMPERATURE AND THE LAST 15 YEARS FOR PRECIPITATION. PNA - PACIFIC NORTH AMERICAN TELECONNECTION PATTERN. QBO - QUASI-BIENNIAL OSCILLATION - AN OSCILLATION OF THE WIND IN THE LOWER STRATOSPHERE BETWEEN EASTERLY AND WESTERLY WHICH REVERSES ON A NEARLY- 2 YEAR TIME SCALE. QBO IS ONE OF THE MOST REGULAR OSCILLATIONS KNOWN. SMLR - SCREENING MULTIPLE LINEAR REGRESSION - A TECHNIQUE WHICH SELECTS THE BEST SET OF PREDICTORS - FITTING THEM TO THE OBSERVATIONS TO CREATE EQUATIONS WHICH CAN BE USED TO MAKE PREDICTIONS. SOUTHERLY WIND - WIND BLOWING FROM SOUTH TO NORTH. STATISTICAL PREDICTIONS - PREDICTIONS BASED MAINLY ON LARGE OBSERVATIONAL DATA SETS. CCA - OCN - SMLR - CAS - CA ARE EXAMPLES OF THESE. TELECONNECTIONS - THESE GIVE THE HISTORICAL RELATIONSHIP BETWEEN A GIVEN POINT AND ALL OTHER POINTS OVER A LARGE AREA - LIKE THE NORTHERN HEMISPHERE - FOR A GIVEN TIME OF THE YEAR. THE POINTS ON THE MAP USUALLY CONSIST OF A SET OF MORE OR LESS EVENLY SPACED LOCATIONS CALLED GRID POINTS. TREND - AT A GIVEN LOCATION AND TIME OF YEAR - THE DIFFERENCE BETWEEN THE AVERAGE OF THE MOST RECENT 10 (15) YEARS OF OBSERVATIONS OF T (P) AND THE CLIMATOLOGY. WESTERLY WIND - WIND BLOWING FROM WEST TO EAST. ZONAL FLOW PATTERN - OCCURS WHEN 500-HPA CONTOURS LIE IN AN EAST-WEST DIRECTION PARALLEL TO LATITUDE CIRCLES WITH NEARLY PURE WEST-TO-EAST FLOW. -------------------------------------------------------------------------------- FOR A DESCRIPTION OF THE STANDARD FORECAST TOOLS - THEIR SKILL - AND THE FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT: HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/DISC.HTML (USE LOWER CASE LETTERS) INFORMATION ON THE FORMULATION AND SKILL OF THE CAS FORECASTS MAY BE FOUND AT: HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWER CASE LETTERS) NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR VALID PERIODS. WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM RANGE FORECASTS SHOULD BE CONSULTED. THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT MONTH ON JANUARY 20 2005. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$